substr adapters

c4::to_substr() and c4::to_csubstr() are used in generic code like c4::format(). More...

Topics
	create substrings from a char literal
	create substrings from C strings
	neutral version for use in generic code

Detailed Description

c4::to_substr() and c4::to_csubstr() are used in generic code like c4::format().

They enable the user to provide an entry point for the construction of substrings from custom types.